Spurious response computer



Jan. 25, 1949.

W T. DOYLE SPURIOUS RESPONSE COMPUTER Filed Aug. 21, 1947 SPURIOUSRESPONSE COMPUTER INVEN TOR. William 2' 00 Earl R. 80%: flaw AttorneyPatented Jan. 25, 1949 2,459,799 SPURIOUS RESPONSE COMPUTER William T.Doyle, Albertson, N. Y., and Earl R. Baker, Delta, 0010.

Application August 21, 1947, Serial No. 769,967

4 Claims. (01. 235-83) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 3'70 0. G. 757) This invention relates tocalculator-sand more particularly to a computer for aiding a radiolistener in distinguishing between true responses and spuriousresponses.

There are many situations, in the art of radio signaling, where it isdesired to know the exact frequency of an incoming radio signal. In thesimplest type of equipment using only tuned radio frequency stages, theincoming signal is detected at only one point in the receiver tuninggamut. Such simple receivers, however, when designed to amplifysufliciently a very weak .signal, are very large and bulky, and arerelatively diflicult to operate and use. As a consequence, it has longbeen a practice to employ superheterodyne receivers which utilize alocal oscillator to generate a local signal which is mixed with theincoming signal to produce an intermediate frequency. The intermediatefrequency may be easily amplified, and then rectified to obtain thedesired modulating intelligence.

Use of a local oscillator, while solving the amplification problem,introduces a new problem in the form of spurious responses, which arisefrom the presence in the locally generated signal of numerous harmonics.Such harmonics, as well as the oscillator fundamental, mix, both aboveand below, with the incoming signal to produce the intermediatefrequency to which the receiver is tuned. Thu-s, as an example, for anoscillator in which all harmonics up to the fifth are strong enough toproduce a detectable output, there are, for a single given incomingsignal, ten responses appearing at ten different points on the receivertuning scale. The receiver operator is faced with the problem ofdetermining which one of these ten responses is the true signal, 1. e,the result of mixing with the proper oscillator harmonic (generally thefirst or fundamental), and in the proper manner. Whi e the diiiicultycan be lessened by insertin R. F. tuning sta es in front of the mixer,very strong signals will pass through the R. F. stages in spite ofanti-tuning in such stages. The receiver operator must, therefore, beprepared to cope with a plurality of responses to the same signal, onlyone of which is the true response.

It is an object of this invention to provide a computer, by means ofwhich the true response may be quickly discerned from among a pluralityof radio responses received.

It is another object of this invention to provide a computer by whichthe true frequency of a signal may be quickly and accurately calculatedfrom any two responses to that signal, whether or not the true signal isamong the two above mentioned responses.

It is another object of this invention to provide a calculator whichwill quickly indicate where all spurious responses may be expected froma predetermined incoming signal.

An example of such a calculator constructs for use with a particularheterodyne receiver will now be described. From this description theprinciples of the calculator will be readily understood and it will bemanifest how similar calculators may be constructed for any givensuperheterodyne receiver. In the equations to be set up below, thefollowing nomenclature will be employed:

f-fundamental frequency of local oscillator.

s-frequency of incoming signal.

R-scale reading on receiver (oscillator) tuning dial.

aany integer from 1 through 5, representing the ordinal of a particularharmonic of the local oscillator.

With this condition the reading R coincides with the actual frequency 3of the incoming signal.

Inasmuch, however, as the incoming signal may in fact mix either aboveor below the local oscillator, and inasmuch as it may mix 'with anyharmonic of the local oscillator from the first to the fifth, a receiverresponse will be obtained whenever the local oscillator is tuned so thatthe following relation is fulfilled:

Expressed in terms of dial reading R rather than oscillator frequencythis equation becomes:

s=a/2(R 30) 5530 (First equation) Conversely, solving for dial readingR, the equation becomes:

R=2/a(s:30) +30 (Second equation) Basically, the calculator of thisinvention is designed to solve the last two equations set forth above.In the construction of the calculator, a

iilerent calculating member is employed for each harmonic oftheoscillator up to five, higher harmonics-Being of insufficientstrength to proona pin l6. means for solving a different equation,depending duce detectable responses. For each harmonic, a pair iofscales is laid out on a common scale member." .One of these scalesrepresents the signal cf teqiiency, s; the other represents the dialreading, Observation of the two equations underconsideration shows thatthere are two values of s for each R, and two values of R for each s. Acursor is mounted to slide along the twoscales on the scale member. Tosolve the first equation, a first single index is marked on the cursor,registering with the dial read ing scale. Cooperative with this index is'a first pair of indices which register with the signal frequency scale.Thus by setting the single index opposite a given dial reading, R, thetwo signals, s," which could produce that response are found, in'so faras any given oscillator har-- monic. a, is concerned. This correspondsto a solution of the first equation with a held constant.

It ispreferred in the practice of this invention to employ the samecursor in the solution of the second equation. To this end a secondsingle index is marked on the cursor registering with the signalfrequency scale. Cooperating with this index is a second pair of indiceswhich register with the dial reading scale. With this set of indices,the second equation may be solved, for any given value of a from one tofive, it being understood that there are five such scale members, eachindependently cooperative with the cursor., 7

The computer may be conveniently constructed of a plurality of disks ofdecreasing diameters laid one on top of the others and pivotally mountedat the disk centers. Each disk contains a pair of scales, correspondingto a predetermined harmonic from one to five, one of each. pairrepresenting dial reading, R, the other representing signal frequency,3.

The cursor is preferably diametrically disposed across the disks andpivotally mounted thereon at the disk centers. To avoid confusion, theindices for solving the first equation are marked so that the singleindex, registering with the dial reading scale, occupies one radius ofthe diametral cursor, while the double indices, which register with thesignal frequency scale, occupy the other radius of the cursor. Thisdisposition of the cooperating indices permits of a, series of slots inone radius of the cursor which register respectively withthe five 'dialreading scales, and a series of slots in the other radius of the cursorwhich register with the five signal frequency. scales. On the edge ofeach slot are marked the appropriate indices.

Solution of the second equation is conveniently provided .by marking thesingle index on the slots registering with the signal frequency scalesand the double indices on the slots registering with the dial readingscales.

A particular calculator constructed in accordance with the teaching ofthis invention will now be described with reference to the accompanyingdrawing, wherein:

Fig. l is a flat view of one side of the calculator, and

Fig. 2 is an edge view of thecalculator taken along line 22 of Fig. 1.

In the drawing there is shown a plurality of flatdisks ll, [2, l3, l4,and I5, of progressively decreasing diameters, placed-one on top of theothers, and pivotally mounted at their centers Each of the disksrepresents the on the oscillator harmonic, a, involved. The

equations where a equals one are solved on the inner disk 55, withhigher harmonics proceeding outwardly to the outer. disk 2%, asindicated by the harmonic numerals l'i, which are marked on a diametralcursor l8 pivoted to the disks by the pin IS.

The visible edge of each of the disks 5 it thru [5 has marked thereon apair of complementary scales. The other of these scales, for example thescale 2! on the disk H, represents the signal frequency 8, in the abovementioned equations. The inner of the circular scales, for example scale22 on the disk ii, reading R on the tuning dial of the receiver.

For solving the second of the equations, the cursor I8 is provided withan arcuate slot 23 registering with the scale 2i. At the outer edge ofthe slot 23 is placed an index in the form of radial, single headedarrow 24. In the opposite radius of the cursor l8 are cut a pair ofarcuate slots 25 and 26, each registering with the dial reading scale22. If desired, the slots 25 and 28 could be joined into a singlearcuate slot, this being merely a matter of design appearance. Doubleindices in the form of single headed arrows 2? 28 are provided at theinner edge of the slots 25 and 26, respectively. The double indices 2?and 28, which register with the dial reading scale 22, are used incooperation with the single index 24, which registers with the signalfrequency scale 2!, to provide a solution for the second equation, for agiven oscillator harmonic, in this case the fifth.

In a similar manner the arrows Zia, 21 21c, and EM cooperate with thecorresponding arrows of the series represented by the numerals 28 and 24to give a solution for the fourth, third, second, and first(fundamental) harmonics, respectively, of the oscillator, by cooperatingwith the respective disks 12, I3, [4, and i5.

Solution of the first equation is efiected in fundamentally the samemanner, except that a single index 3| is provided opposite only one ofthe dial reading scales, namely, the scale for the second harmonic onthe disk It. Instead of providing single indices opposite each of thedial reading scales, means are provided for lining up the several disksH thru Hi. This means assumes the form of radial lines 32, marked acrossthe scales of each of the disks. When the radial lines 32 are aligned asshown in'Fig. 1, all of the dial reading scales 22 occupy the sameangular position, and the single index 3i may then be used for each ofthe disks ll thru 15.

To distinguish the indices which solve the second equation from thosewhich solve the first equation, the former are provided with singleheads, as mentioned above, while the latter have double heads as seen inthe double headed arrow 3!. On the upper radius of the cursor is, eachof the slots 2-3 has marked on the edge thereof double indices in theform of pairs of double headed arrows, represented by the arrows 33 and34, cooperating with the signal frequency scale 2! of the fifth harmonicdisk ii. The double headed arrows 33 and 34 cooperate with the doubleheaded arrow 3! in the solution of the first equation, in the samemanner as the single headed arrows 2'! and 23 cooperate with the singleheaded arrow 24 in the solution of the second equation.

The particular computer shown in Fig. 1 is designed for use with areceiver having the properties discussed above; namely, one designed tohave the second harmonic of the oscillator mix 30 megacycles below theincoming signal.

Ksgshow'xrin Fig. 2; the calculator may conveniently be made doublefaced; with the reverse sidesmarked for" use with a receiver-- l'ravingdifferent properties than those discussed hereinbef'ore. In this case;the reverse cursor 4i, used with the reverse face; is preferablysecuredat each end to the obve'se cursor ifi by suitable means such asgimlet eyes 42 Use or the computer A first example of using the computerof the instant invention willgnow'ber described. Assume that responsesto a particular signal have been obtained on the" receiver at" the 440megacycle point, and at the 410 megacycle point. The dial reading scalesofieachcflthedisks H'thru h": are first adjusted by aligning the radiallines 32. Clamping the disks together with. one hand, the operatorrotates the cursor l8 until the double headed arrow 3i is opposite the440 figure on the dial'reading, scale of the disk M, as shown in Fig. l.All"s'ign'als which could'produce this response are then found oppositethe ten double headed arrows, exemplified by the numerals 33 and 34.These signals are noted by the operator as:

H5 545 235 I90 380 850 44!! 995 585 L055 The cursor is then turned untilthe double headed arrow 3| is opposite M9 on the dial reading scale. Theten signal frequencies which could cause this response are then notedas:

I60 600 220 I30 350 190 M0 920 540 980 Comparison of the two lists ofsignals shows that only one signal frequency, namely 790, is common tothe two dial readings. The true frequency of the response is thus foundto be 790 megacycles.

Now, assume that it is desired to know all the dial reading points atwhich responses from the 790 megacycle signal might be detected. Each ofthe disks I! through 15 is rotated until the several arrows 24 areopposite the 790 point on the signal frequency scales 2|. The innerscale, on disk i5, does not extend as far as 790 megacycles, therebyindicating that the oscillator fundamental can not be brought within 30megacycles of the incoming signal, and hence cannot produce a responseon the receiver dial. The eight responses are found opposite the singleheaded arrows 21, 21a, 21b, and 210, and the corresponding arrowsrepresented generally by the numeral 28. These responses are found toThese are the eight points on the dial where the 790 megacycle signalcan be received. Seven of these will be spurious responses, only the 790reading being genuine.

The frequency separation in megacycles between an upper mixing and alower mixing for any given harmonic is given by the several lar disks of6. numerals 44, marked on the cursor l8 adjacent the harmonic dish towhich the figure applies.

In determining the true signal frequency from. a set of any two responsereadings as outlined in the first example above, it is essential thatthe ngs represent an upper mix i and a lower ng of the with an oscilltor harmonic. If both readings result from an upper mixing or if bothreadings result from lower mixing, the solution will be ambiguous inthat there will be two frequencies appearing in both lists, either ofwhich could have caused that particular set of responses. In this eventit is necessary to obtain. further responses to the same signal until aresponse is obtained which is the result of a that tbeen proi ded acomputer whereby the true si type of superheterodyne receiver. It willbe understood that various modifications and changes may be made in thisinvention without departing from the spirit and scope thereof as setforth in the appended claims.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

l. A calculator comprisin a plurality of members mounted for movementrelative to each other, each of said members having a pair ofcomplementary scales marked thereon, and a cursor mounted for movementacross members having a series of single indices thereon cooperative,respectively, with the first of each of said pairs of scales, and aseries of pairs of indices thereon cooperative with the second of eachof said pairs of scales.

2. A calculator comprising a plurality of circu-- progressivelydecreasing diameters pivotally mounted concentrically for relativerotation each with respect to the others, pairs of circular scalesmarked adjacent the edges of each disk, a cursor disposed diametricallyacross the faces of said disks pivotally mounted on the axis of saiddisks, said cursor having a first series of single indices markedthereon, cooperative with the first of said pairs of scales, and a firstseries of spaced, double indices marked thereon cooperative with thesecond of said pairs of scales.

3. A calculator comprising a plurality of circular disks ofprogressively decreasing diameters pivotally mounted concentrical forrelative rotation each with respect to the others, pa'rs of circularscales merited adjacent the edges of each disk, a cursor di poseddiametrically across the faces of said disizs pivotally mounted on theaxis of said disks, cursor having a first series of single indicesmarked thereon cooperative with the first of said pairs of scales, afirst series of spaced, double indices marked thereon cooperative withthe second of said pairs of scales, a second single index marked thereoncooperative with the second of said pairs of scales, a second series ofdouble indices marked thereon cooperative with. the first of said pairsof scales, and radia lines On said disks by means of which said disks beplaced in a predetermined relative position.

4. A calculator comprising a plurality of circular disks ofprogressively decreasing diameters pivotally mounted concentrically forrelative rotation each with respect to the others, pairs of circularscales marked adjacent the edges of each disk, a cursor disposeddiametrically across the faces of said disks pivotally mounted on theaxis of said disks, said cursor having a first plurality of arcuateslots cut therethru on one radius thereof, said slots registering,respectively, with the first of each of said pairs of scales, and asecond plurality of arcuate slots cut therethru on the other radiusthereof, said last mentioned slots registering, respectively, with thesecond of each of said pairs of scales, a first series of single indicesmarked on said cursor at the edges of said first pllu'ality of slotscooperative with the first of said pairs of scales, a first series ofspaced double indices marked on said cursor at the edges of said secondplurality of slots cooperativewith the second of said pairs of scales, asecond, single index marked on said cursor at the edge of one of saidsecond plurality of slots cooperative with the second of said pairs ofscales, a second series of spaced double indices marked on said cursorat the edges of said first plurality of slots, cooperative with thefirst of said pairs of scales, and a series of radial index lines markedacross said scales for use in arranging said disks in a predeterminedrelative position.

WILLIAM T. DOYLE. EARL R. BAKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,429,264 Wright Sept. 19, 19221,520,105 Bicknell Dec. 23, 1924 1,780,078 Hite Oct. 28, 1930 2,048,819Russ July 28, 1936

